1. Field of the Invention
This invention relates in general to orifice fitting equipment for connection into a pipeline for measuring gas flow by means of monitoring a pressure drop through an orifice plate, and in particular to a means for gaging the width of the seat slot that receives the orifice plate and plate carrier.
2. Description of the Prior Art
An orifice fitting is an assembly used to measure gas flow. The fitting includes a body which has a passage for connection into a gas pipeline. The passage has a seat slot which is perpendicular to the gas flow. The seat slot has opposed seat faces.
A plate carrier will move from an upper chamber down into the seat slot. The plate carrier has a circular opening contained in an orifice plate. The orifice plate has an opening through which the gas will flow. The pressure drop that flows through this opening will be monitored. Measurement equipment will be able to determine the gas flow rate based on the pressure drop.
It is important to have a good seal, particularly at the downstream seat face. If the plate carrier does not seal properly in the seat slot, leakage will occur past the plate. This leakage can provide erroneous readings. While the width of the seat slot will be manufactured to a specified tolerance, during pressure testing, portions of the slot width may exceed and remain permanently in excess of the tolerance. Currently, there is no method to determine the width of the seat slot while the orifice fitting is connected into the pipeline.